Interesting enough to me, and pretty relevant to a claim like "book-writing is rarely commercially worthwhile". No "points scored" against the publishing industry, but point-scoring is for shallow people.
For publishing, I wonder how many copies of little-bought books are read, and how many are printed -- both probably quite different to the number sold. And I also wonder how the outcome distribution compares to venture capital outcomes, and what predictor variables are useful. "Harry Potter" is a famous case of prediction being difficult (or at least badly done?) but you can probably get some signal from author (writing history, other celebrity), genre.
what counts as a book? If a book thats not published is a book, what about a collec5uon of my notes and memoirs on my blog. It got read by loads of people, should it count to the statistics?
This ambiguity around what a book is seems like an artificial one. Go to a bookstore or view the catalog in Apple Books. Those are books, even the $0.99 micro stories one might find on, e.g., Kindle. Anything else might be a book, but probably not in a way that is useful or constructive to analyze in the context of sales.